Communication applications in today's business and private environments are ubiquitous and offer a wide variety of different services, such as e-mail services, web browsing, telephony and video conferencing. With the different communication applications different resource requirements emerge. For example an e-mail application requires a transmission of data from a sender to a recipient, but generally strict time constrains are not imposed on the data transmission. However, a voice or video communication application requires a certain minimum data throughput and is time sensitive, i.e., delays in the transmission of information lead for example to voice or video dropouts and corresponding inconvenience.
Further, while traditional circuit switched networks generally provide a dedicated connection for a certain application, such as a telephone conversation or video conference, packet switched or connectionless networks do not provide such dedicated communication line, but may for example route a sequence of data packets from a source to a destination, possibly over varying paths. A delay of one or more of these packets during transmission will cause problems at the destination, as the application has to wait for the delayed data packet before continuing the service.
Obviously such characteristics of networks are undesirable, raising the demand for mechanisms to assure certain minimum qualities of a communication in such networks. Quality of service (QoS) is a term referring to required characteristics of a communication application. For example a quality of service characteristic of a video conference could be constituted by a certain minimum data throughput and a certain maximum delay of data transmissions. In order to meet quality of service requirements, a communication application may signal corresponding information prior to establishing a communication link between the communicating entities. The network in response thereto establishes, if possible, a corresponding communication link maintaining the requirements specified.
Communication resources may be reserved for a communication application upon initialising the communication or a data flow associated with the application. This reservation may address the quality of service requirements stated by the communication application. The resources may be reserved once by a central authority assigning the required resources to the communication link or data flow, or the communication resources may be assigned to the communication dynamically on a distributed bases at each network node of the communication network transmitting or relaying the communication link or data flow. A new data flow can only be admitted, if sufficient communication resources are available.
It is therefore required in this case that each network node maintains information on previously allocated communication resources.
However, with a potentially large number of different data flows each node must store a correspondingly large amount of data of the requirements for each flow.